A light detection device including: a Fabry-Perot interference filter having a first mirror and a second mirror, a distance therebetween is variable; a light detector for detecting light transmitted through the Fabry-Perot interference filter; a package accommodating the Fabry-Perot interference filter and the light detector; and a light transmitting unit arranged on an inner surface of the package so as to close an opening of the package is known (see Patent Literature 1, for example).